ABSTRACT
The foot can be regarded as a reference for the human aging process. A lack of walking or exercise results in poor development of the foot muscles, which increases the risk of falling and also increases the flatfooted population. Analyzing the complexity of postural dynamics at different time points is helpful when assessing the balancing ability of participants. This study measured the center of pressure (COP) signals from standing participant, to distinguish differences in balancing ability for flatfooted people versus those with normal feet.
An experiment was conducted to determine changes in the COP. Participants were asked to stand on a platform for 65 s with their eyes open or closed. We measured changes in the COP distribution from front-to-back (anteroposterior, AP) and side-to-side (mediolateral, ML), respectively. The method of empirical mode decomposition (EMD) was used to reconstruct short-term COP signals, and the concepts of sample entropy (SampEn) and multiscale entropy (MSE) were applied to analyze the complexity of balance. Balance was represented by a complexity index value, C I.
Nineteen participants (11 men and 8 women) aged 22 to 42 years (mean age 29.74 ± 6.04 years) were assessed. The results showed that the CI for the AP direction was lower for flatfooted participants with open eyes, compared with participants with normal feet (4.92±0.55 and 5.26±0.58, respectively). Flatfooted participants with closed eyes also showed lower CI compared with the comparison participants (4.33 ±0.57 and 5.11±0.58, respectively). We also compared the results 77of our MSE analysis with nine traditional stabilogram metrics. The P-value for the eyes-open condition was .203 (not significant) and that for eyes-closed was .01. This result indicated a significantly lower CI among flatfooted participants compared with normal-foot participants for the eyes-closed condition.
The MSE method of analysis can clearly distinguish between normal feet and flatfeet. Further experiments will be conducted to identify various symptoms of flatfeet. To help elderly avoid falling down and to alleviate their symptoms, strategies will be developed to improve their balance control.
